Field
The disclosed technology generally relates to forming a semiconductor structure and more particularly to forming a stack of layers of a semiconductor structure using a sacrificial layer.
Description of the Related Technology
Semiconductor technology continues to integrate increasingly smaller feature sizes, and correspondingly continues to increase the device density and functionality per unit area. Increasing device density in turn enables proportional reductions in device footprint and cost. The trend of downscaling, however, continues to introduce new and previously unmet challenges with each successive generation.
Generally, semiconductor device fabrication involves formation of various semiconductor structures by patterning, e.g., by forming (e.g., depositing) and removing (e.g., etching) one or more layers of materials. When forming a semiconductor structure having a plurality of layers of materials, each layer may be selected to provide a particular functional feature within the semiconductor structure. Individual layers are generally deposited during fabrication of the semiconductor structure to form various functional structures. For example, a metal layer may be deposited to form, e.g., metallization and electrical contacts, among other electrically conducting structures, while a dielectric layer may be deposited to form, e.g., isolation structures and spacer structures, among other electrically insulating structures.
Generally, smaller devices are more prone to being detrimentally affected by defects, which may lead to, e.g., increased current leakage and charge trapping. Even relatively small variations in the nanometer-scale of the material structure/composition and the interfaces between the layers may substantially degrade the device performance. As a result, the smaller feature sizes increase the need for advanced fabrication techniques with reduced defects.
Physical vapor deposition (PVD) is a fabrication technique used to deposit thin layers in most semiconductor devices by condensation of a vaporized target material onto a substrate. To meet the increasing needs of physical scaling of semiconductor devices, there is a corresponding need to improve PVD techniques for fabrication of various structures by depositing thin films with improved purity, improved thickness control and smoother interfaces between adjacent layers.
There is therefore a need for improved techniques for forming semiconductor structures comprising a plurality of layers using PVD.